Chicken DNA may unlock secrets of evolution

Scientists today unveil the secrets of the bird that feeds the planet. More than 170 researchers from 49 institutes in 12 countries report in Nature that the completed DNA sequence of Gallus gallus, the red jungle fowl, ancestor of all domestic chickens, could throw light on human evolution and lead to tastier eggs and better farmyard fowl.

The DNA sequence confirms that humans and chickens share 60% of their genes. The genetic evidence also reasserts that all life on the planet shares a common origin, and that in the course of 500m years of evolution, nature has used the same genes over and over again, but in subtly different ways.

Scientists hailed the completion of the genome as a step forward in evolutionary research because the chicken is humankind's most distant warm-blooded relative to be sequenced so far.

In nine hectic years, geneticists have assembled the entire DNA recipes for microbes such as bubonic plague, tuberculosis and yeast; complex creatures such as the fruit fly, the nematode worm and the malarial mosquito; rice, and a tiny weed called thalecress; rats, mice and humans; and a Japanese restaurant favourite the puffer fish.

But the chicken is the first bird to be sequenced, so its DNA will throw light on an estimated 9,500 other species of bird. Birds are the closest surviving relatives of the dinosaurs, which disappeared from the fossil record 65m years ago. Birds and mammals shared their last common ancestor 300m years ago, whereas rodents and humans - which share 88% of their genes - are descended from a common ancestor that perhaps scuttled between the feet of the dinosaurs a mere 70m years ago.

"Looking at mice, rats, and now the chicken, all of which are removed from us at different distances, is like peering through a collection of evolutionary lenses: each brings contrasting aspects of human biology into sharp focus," said Chris Ponting, of the Medical Research Council in Britain.

"The chicken is really in an evolutionary sweet spot," said Richard Wilson, director of the international chicken genome sequencing consortium at Washington University school of medicine in St Louis, Missouri.

"It's just the right evolutionary distance from all the other genomes we have already, to provide us with a great deal of fresh insight into the human genome."

The sequence - freely available to biologists around the world - will keep biologists busy for decades trying to understand why chickens have roughly the same number of genes as humans - somewhere between 20,000 and 25,000 - even though the entire genome is far smaller.

Gallus gallus has only about 1bn base pairs of "letters" in its genetic code, whereas Homo sapiens has 2.8bn.